SCIENCE WATCH

SCIENCE WATCH; Cosmic 'Black Dust'

Published: September 1, 1987

A new analysis of cosmic dust particles found in the ice of Greenland confirms not only that they are extraterrestrial and the richest such deposits ever discovered on Earth but also that they have largely survived in pristine condition, a team of French scientists has reported.

The deposits of the particles were discovered north of Sondrestromfjord in 1984 by French, American and Danish scientists. In a preliminary study reported last year, the tiny black particles were determined to be extraterrestrial in origin.

Previously, the major site of cosmic grains has been the ocean floor. The new report, published recently in the journal Nature, concluded that the Greenland ''black dust,'' as the cosmic grains are called by scientists, were purer extraterrestrial samples in part because they had not been exposed to the chemical effect of prolonged submersion in the ocean.

The scientists also determined that a ''surprisingly high abundance'' of the Greenland particles were extremely small (literally dust-size grains) and this made it possible for them to reach the Earth's surface without having been melted by frictional heating in the atmosphere.